Method and apparatus for protection of electronic media

ABSTRACT

Described is a system and method for providing protection of media by the detection of unauthorized client behaviors and the communication of the unauthorized client behaviors to augment the invention&#39;s detection abilities. A variety of detectors are sent to a client process and the responses are evaluated to detect the presence of an unauthorized software behavior on the client. Unauthorized behaviors include alteration of a client process as well as simultaneously running processes that might enable unauthorized copying of protected media. Communication of unauthorized software behaviors includes sharing of memory detectors among servers on a network, and the sending of memory detectors to other clients to detect previously unseen unauthorized behaviors on the other clients.

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/255,851 filed on Dec. 14, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates to computer readable data storageand more particularly to copy protection and data integrity of computerreadable data.

BACKGROUND OF THE INVENTION

[0003] There has been much attention focused on the protection ofcopyrighted computer readable media, including image, audio, and video,through tests on the integrity of the media and the legality of thesoftware with which the media is associated.

[0004] Traditional copy protection methods that secure electronic mediasuch as images, audio, and video include a variety of methods such asstandard encryption and data marking.

[0005] Standard encryption technologies have been used in the protectionof electronic media sent over networks. These technologies encrypt astream of data on the server side and then decrypt the data on theclient side, in order to deter the understanding and the stealing of thedata by a third party who has access to the network.

[0006] The process of “watermarking” electronic media has been anothersecurity measure implemented to deter the frequency of illegal mediacopying. Typically, watermarking tools place transparent and uniqueidentifiers onto visual content and then enable the watermarked imagesto be more tightly controlled by their creators.

[0007] Other copy protection schemes have focused on actively protectingmedia from unauthorized viewing or copying, in addition to simplylabeling the media with ownership and copyright information. Suchschemes typically include the use of secure containers for electronicmedia and some form of encryption.

[0008] There has even been an attempt recently to establish a GlobalUnique Identifier that would allow media providers to link SecureDigital Music Initiative (SDMI) files to a specific computer, andthereby limit a user's ability to copy the files.

[0009] Moreover, artificial immune systems (AISs) have been designed tonotice malign virus (worm, Trojan horse) entry into a computer or acomputer network.

SUMMARY OF THE INVENTION

[0010] Briefly stated, the present invention is a system, an article,and a method to detect unauthorized client behaviors and thecommunication of the unauthorized client behaviors. A variety ofdetectors are sent to a client process and the responses are evaluatedto detect the presence of an unauthorized software behavior on theclient. Unauthorized behavior includes alteration of a client process aswell as simultaneously running processes that may enable unauthorizedcopying of the protected electronic media. Communication of unauthorizedsoftware behavior includes sharing of detectors among servers on anetwork, and the sending of detectors to other clients to detectpreviously unseen unauthorized behaviors on the other clients.

[0011] In accordance with one illustrative aspect of the presentinvention, a method includes sending at least one detector to a clientprocess, receiving a response to the detector from the client process,detecting a presence of an unauthorized software behavior on the clientbased upon the response, and updating a database of detectors for apreviously unseen and unauthorized behavior of the process such that thedatabase evolves over time.

[0012] In another illustrative aspect of the present invention, a methodincludes exchanging sets of memory detectors between servers during anupdate period, evaluating the received set of memory detectors against arecipient's self database and a set of matching rules, discarding memorydetectors in the received set of memory detectors that match a detectorin the recipient's self database, and merging the remaining memorydetectors with the existing memory database.

[0013] In another illustrative aspect of the present invention, a systemincludes a server to send media to a client; and an application(computer program) to perform actions when executed that include sendinga detector to the client, receiving a response to the detector from theclient, detecting a presence of an unauthorized process behavior on theclient based on the response and a matching rule associated with thedetector, and updating a database of detectors for a previously unseenunauthorized process behavior on the client such that the databaseadapts based on the response.

[0014] In still another illustrative aspect of the present invention, amachine readable medium provides instructions which, when executed by atleast one processor, cause the processor to perform operations thatinclude sending at least one detector to a client process (or executingprogram), receiving a response to the detector from the client process,detecting a presence of an unauthorized software behavior on the clientbased upon the response and a matching rule that is associated with thedetector sent; and updating a database of detectors for a previouslyunseen and unauthorized behavior of the process such that the databaseadapts the detector based upon the detector response.

[0015] Other features and advantages of the present invention willbecome apparent from the following Detailed Description of the Inventionread in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Non-limiting and non-exhaustive embodiments of the presentinvention are described with reference to the following drawings. In thedrawings, like reference numerals refer to like parts throughout thevarious figures unless otherwise specified. The order of description inflow diagrams should not be construed as to imply that these operationsare necessarily order dependent.

[0017] For a better understanding of the present invention, referencewill be made to the following Detailed Description of the Invention,which is to be read in association with the accompanying drawings,wherein:

[0018]FIG. 1 is a block diagram of an embodiment of the presentinvention implemented by a server and a client, coupled through anetwork, to detect unauthorized software execution;

[0019]FIG. 2 is a block diagram of an embodiment of a server computer asportrayed in FIG. 1;

[0020]FIG. 3 is a block diagram of an embodiment of a client computer asportrayed in FIG. 1;

[0021]FIG. 4 is a diagram of an embodiment of a detector type;

[0022]FIG. 5 is a block diagram of an embodiment of the presentinvention implemented by a server and a client, coupled through anetwork, in which the client includes a detector generator;

[0023]FIG. 6 is a block diagram of an embodiment of the presentinvention implemented by a server and a client, coupled through anetwork, having a client generation of audited system calls;

[0024]FIG. 7 is a diagram of an embodiment of a detector type withprocess data identity fragments;

[0025]FIG. 8 is a block diagram illustrating an embodiment of ArtificialEpidemiological Control (AEC) component;

[0026]FIG. 9 is a flow diagram of an embodiment of an Artificial ImmuneSystem (AIS) process;

[0027]FIG. 10 is a flow diagram illustrating an embodiment of a processof updating detector life-cycle information;

[0028]FIG. 11 is a flow diagram illustrating an embodiment of an AECprocess to share information about unauthorized client process behaviorsto augment detection of apparent widespread unauthorized client processbehaviors;

[0029]FIG. 12 is a block diagram of an embodiment of a multi-servercommunication AEC architecture to enable servers coupled to a network tocommunicate portions of stored memory as memory detector set(s) to othernetwork coupled server(s);

[0030]FIG. 13 is a block diagram of an embodiment of an operatingenvironment to evaluate received memory detectors; and

[0031]FIG. 14 is a block diagram of an embodiment of an operatingenvironment with an AIS and AEC, in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0032] Throughout the specification, and in the claims, the term“connected” means a direct electrical connection between the things thatare connected, without any intermediary devices. The term “coupled”means either a direct connection between the things that are connected,or an indirect connection through one or more passive or activeintermediary devices. The meaning of “a,” “an,” and “the” include pluralreferences. The meaning of “in” includes “in” and “on.” Additionally, areference to the singular includes a reference to the plural unlessotherwise stated or inconsistent with the disclosure.

[0033] Briefly stated, the present invention is directed to a method andsystem of copy protection and data integrity for computer readablemedia. Protection of computer readable media includes detection ofunauthorized software behavior, and communication of the detection ofunauthorized software behavior. Unauthorized behaviors includealteration of a client process as well as simultaneously runningprocesses that may enable unauthorized copying of protected media.

Artificial Immune System (AIS) Operational Environment

[0034] The present invention has identified that a computer systemimplemented analogy of a biological system to respond to a foreign bodyinfection, termed herein an Artificial Immune System (AIS), may beemployed to monitor software behavior for unauthorized softwareoperations such as copy protection and data integrity. The AIS ispremised on the concept that both living entities and computersencounter continuously changing deleterious foreign matter against whichthey must defend themselves. In the case of living entities, thatforeign matter includes viruses, bacteria, and other pathogens thatevolve through a process of natural selection. Living entitiesaccomplish this feat by recognizing the “self” (e.g., all the proteinsthat constitute the living entity) and considering things that falloutside of this category to be potentially harmful. In the case ofcomputers, that foreign matter includes viruses, worms, and Trojanhorses that are generated within a computing system and may spread fromone computer system to another, leaving a trail that may cause computersystem software to be infected and to execute abnormally. In the presentinvention, a computer system recognizes unauthorized copying and storingof data through the determination of abnormal client process behavior.

[0035] Referring to FIG. 1, server-based detector system 100, includes aserver 102, a network 104, a client 106, detector(s) 110, andresponse(s) 112. Server 102 includes an AIS detection unit 114. Client106 includes an executing client software process 108, which is to beexamined, and client presenter 116.

[0036] The server 102 is coupled to network 104 and is described in moredetail with reference to FIG. 2 below. Client 106 is also coupled tonetwork 104 and is described in more detail with reference to FIG. 3below.

[0037] In the embodiment portrayed with reference to FIG. 1, network 104can employ any form of network media for communicating information fromone electronic device to another. Also, the network 104 can include theInternet in addition to local area networks (LANs), wide area networks(WANs), direct connections, such as through a universal serial bus (USB)port, forms of computer-readable media, or any combination thereof. Onan interconnected set of LANs, including those based on differingarchitectures and protocols, a router acts as a link between LANs,enabling messages to be sent from one to another. Also, communicationlinks within LANs typically include twisted wire pair or coaxial cable,while communication links between networks may utilize analog telephonelines, full or fractional dedicated digital lines including T1, T2, T3,and T4, Integrated Services Digital Networks (ISDNs), Digital SubscriberLines (DSLs), wireless links including satellite links, or othercommunications links known to those skilled in the art. Furthermore,remote computers and other related electronic devices might be remotelyconnected to either LANs or WANs via a modem and temporary telephonelink. A remote computer may act in a number of ways, including as aninternet (content) server or a client with an application program.

[0038] It will be appreciated that network 104 may comprise a vastnumber of such interconnected networks, computers, and routers. Asshown, server 102 and client 106 are in communication through network104, which provides a path between the executing client software process108 and the embodiment of the AIS detection unit 114.

[0039] Server 102 provides access to information, such as streamingmedia, and services through network 104 to client 106. While client 106may be receiving information from server 102, server 102 may alsotransmit through network 104 a series of detectors 110 to clientpresenter 116. Client presenter 116 in turn presents detectors 110 toclient software process 108 residing on client 106. Client 106communicates responses 112 to detectors 110 through network 104 forevaluation by AIS detection unit 114. The communication of detectors 110and responses 112 between client 106 and server 102 may occur withoutthe user's knowledge.

[0040] Referring to FIG. 2, a server 102 enables the operation ofnetwork server 204 on network 104 (FIG. 1) for access by a client, suchas client 106. Accordingly, server 102 enables network server 204 torespond to requests for information by a client software process 108, orother application programs 334 (FIG. 3), which are running on client 106(FIG. 3). For instance, server 102 can stream data, drawings, pictures,figures, graphics, movies, audio files, animations, and the like inresponse to a request for information. These transactions can take placeacross a closed or open network, such as the Internet. The server 102may include many more components than those shown. As illustrated inFIG. 2, server 102 can communicate with a network, via network interfaceunit 266 for use with and according to, communication protocols such asTCP/IP protocol.

[0041] Server 102 in an embodiment includes processing unit 242, videodisplay adapter 260, and a mass memory, all in communication with eachother via bus 264. The mass memory generally includes RAM 244,non-volatile memory, such as a ROM 256, and one or more permanent massstorage devices, such as hard disk drive 252, tape drive, optical drive,and/or floppy disk drive. The mass memory stores operating system 246for controlling the operation of server 102. A general-purpose serveroperating system may be employed, e.g., UNIX, LINUX, WINDOWS NT®, or thelike. Basic input/output system (“BIOS”) 258 is also provided forcontrolling the low-level operation of server 102. The mass memory alsostores program code and data for providing a presence on a network. Morespecifically, the mass memory stores application programs 250, data (notshown), and network server 204. These application programs 250 includecomputer executable instructions which, when executed by centralprocessing unit 242, generate response messages and perform the logicdescribed elsewhere in this specification. The application programs 250include programs that perform logical operations. Server 102 may alsoinclude a Simple Mail Transfer Protocol (SMTP) handler application (notshown) for transmitting and receiving e-mail, a Hypertext TransferProtocol (HTTP) handler application for receiving and handing HTTPrequests, and an HTTP Over Secure Socket Layer (HTTPS) handlerapplication (not shown) for handling secure connections. Server 102 theembodiment includes input/output interface 268 for communicating withexternal devices, such as a mouse, keyboard, scanner, and other inputdevices not shown in FIG. 2. Likewise, server 102 may further includeadditional mass storage facilities such as CD-ROM/DVD-ROM drive 262 andhard disk drive 252. Hard disk drive 252 is utilized by server 102 tostore application programs, databases, and program data used by thenetwork server 204 to be loaded into RAM 244 for execution, and thelike. For example, Detector databases (described in more detail below),audio databases, and image databases, and the like may be stored.

[0042] Server 102 includes AIS detection unit 114 (as described in anembodiment with reference to FIG. 8) and in an embodiment ArtificialEpidemiological Control (AEC) unit 1208 (described with reference toFIG. 12.) Servers that include an AIS detection unit 114 ask questionsof, and receive responses from, clients. These questions take the formof “detectors”, which are any identifying characteristic of an executingprogram.

[0043] Referring to FIG. 3, client 106 includes network interface unit302 for connecting to a LAN, VLAN, or WAN, or for connecting remotely toa LAN, VLAN, or WAN. Network interface unit 302 includes necessarycircuitry for such a connection, constructed for use with variouscommunication protocols including the TCP/IP protocol, the particularnetwork configuration of the LAN, VLAN, or WAN it is connecting to, anda particular type of coupling medium. Network interface unit 302 mayalso be capable of connecting to the Internet through a point-to-pointprotocol (PPP) connection or a Serial Line Internet protocol (SLIP).

[0044] Additionally, modem 330 is in communication with centralprocessing unit 314 via bus 322 and enables server 102 to place a callto or receive a call from a telephone number. Modem 330 may be a wiredand/or wireless telephonic device capable of transmitting voice and/ordata.

[0045] Client 106 includes BIOS 326, central processing unit 314, videodisplay adapter 308, and memory. The memory generally includes randomaccess memory (RAM) 310, read-only memory (ROM) 304 and a permanent massstorage device, such as disk drive 318. The memory stores operatingsystem 312 and other application programs 334, for controlling theoperation of client 106. The memory also includes client softwareprocess 108, and client presenter 116 for managing the informationprovided by server 102 in response to requests by clients 106. Theapplication programs, software processes, and content are stored on acomputer-readable medium. Input/output interface 320 may also beprovided for receiving input from a mouse, keyboard, or other inputdevice. The memory, network interface unit 302, video display adapter308, and input/output interface 320, modem 330 are all connected tocentral processing unit 314 via bus 322. Additionally, modem 330 may bea wired or wireless telephonic device capable of transmitting dataand/or voice communications. Other peripherals may also be connected tocentral processing unit 314 in a similar manner.

[0046] Referring to FIG. 4, an embodiment of a detector 110 includes anillustrative detector 400. Here the detector 400 consists of a sequenceof file system calls generated by an executing program, which can beeither exactly or partially matched by a currently executing program's(or process's) audited file system calls, depending upon the givenmatching executing algorithm (rule).

[0047] Referring again to FIG. 1, one or more matching rules (not shown)are associated with detector 110 and are employed in determining howstringent a given sequence of computer system calls must be matchedbefore a match is validated. For example, for a sequence of eight systemcalls, one possible matching rule is that the sequence matches if any ofsix of the eight calls is matched, i.e. a detector 110 is sent, and areceived response 112 matches. Another possible matching rule is torequire the first six system calls in the sequence included withindetector 400 to match. A matching rule may be employed that describes aset of possible matches, such as:

OPEN/*/READ/CLOSE/READ/WRITE/*/IOCONTROL

[0048] where the ‘*’ denotes that the algorithm classifies a matchregardless of what system call sequence arises after the “OPEN” and“WRITE” system calls in detector 110.

[0049] It will be appreciated by one of ordinary skill in the art thatthe length of a given sequence of system calls within detector 110 maybe any length such as eight. It has been determined that by varying thelengths of a sequence of system calls it may be more difficult todiscern the meaning of detector 110, thereby improving the security, andeffectiveness of the present invention.

[0050] In another embodiment of the present invention, the sequencecalls are numerically encoded and combined into a number fortransmission to and/or storage on client 106. Encoding the sequencecalls is directed at obscuring the meaning of detector 110 further, asthe number may have different meanings based on the algorithm employedto encode the sequence, thus making it more difficult for a client sideuser to determine how the invention functions.

[0051] Encoding schemes for the sequence calls may be implemented in avariety of ways depending upon the number of system calls in a givensequence, the format of the detector rules, and the like. For example, ageneric hashing function may be employed to encode the system callswithin detector 110, without departing from the scope or spirit of thepresent invention.

[0052] Three varieties of detector 110 are illustratively describedherein. One variety of detector 110 is a self-detector. A self-detectoris a system call fragment that is typically located in a completeself-database, i.e., a database that includes a set of possiblesequences of system calls seen in the normal execution of clientsoftware process 108. If a common self-detector is employed as a“behavioral question” to client software process 108 running on client106, client software process 108 is to provide a response that indicatesan acknowledgment that the self-detector has been found in its audit log(not shown).

[0053] Another variety of detector 110 is a memory detector. A memorydetector is a system call sequence that has already been associated withunauthorized software alterations. These detectors are typically takenfrom an AEC database, and are typically employed to detect recurrentunauthorized software alterations.

[0054] Yet another variety of detector 110 is a novel detector. A noveldetector is a system call sequence that is a possible behavioralanomaly, but has not previously been seen. They are employed torecognize new unauthorized software alterations.

[0055] While three varieties of detector 110 have been described above,the present invention is not so limited. For example, detectors composedof only non-system calls, or a combination of system and non-systemcalls, and the like, may be employed, without departing from the spiritor scope of the invention.

[0056] Operationally, server 102 communicates detector 110 to client 106over network 104. Positive or negative responses 112 in turn arecommunicated to server 102, depending on whether the detectors have beenmatched by the audited system call fragments of client software process108 on client 106. The AIS detection unit 114 on server 102 evaluatesclient's responses 112 to determine the authorization status of client'sexecuting software 108.

[0057] If server 102 communicates common self-detectors to client 106,AIS detection unit 114 expects to receive a positive response 112 fromclient 106, thereby confirming the ability of client 106 to respond. Bytransmitting non-self detectors (i.e., memory or novel detectors), AISdetection unit 114 is enabled to test for illegal behavior of clientsoftware process 108. Negative responses to the non-self detectors maybe expected of an authorized client software process 108. Positiveresponses to some non-self, novel detectors may be expected of a clientwith an unauthorized software alteration that has not yet beendocumented. Positive responses to some non-self memory detectors may beexpected in the case of a client that is executing an unauthorizedsoftware alteration documented in the memory database (not shown).Because a client is unlikely to know a priori whether a given detector110 should receive a positive or a negative response, an attempt by auser to alter a client to return a positive or a negative responsewithout authorization is likely to fail, thus increasing the security ofserver-based detector system 100.

[0058] Referring to FIG. 5, the client-side detector generation system500 includes client detector generator 502. Client detector generator502 is in operation executing a program within client 106 that iscoupled to, and communicates with client's software process 108, or itmay be a component of the client's software process 108. The operatingenvironment shown in FIG. 5 operates in substantially the same manner asthe operating environment shown in FIG. 1, except that client detectorgenerator 502 provides “behavioral questions” in the form of self andnon-self (i.e., novel and memory) detectors to client executing program108. Responses 112 from client executing program 108 are communicatedthrough network 104 to AIS detection unit 114.

[0059] Referring now to FIG. 6, sequences of audited system calls 602are communicated through network 104 to AIS detection unit 114. Auditedsystem calls 602 are compared against a client software processself-database (not shown) included in AIS detection unit 114 todetermine if a significant portion of client software execution behavioris abnormal. Audited system calls 602 are transmitted to server 102 byclient's software process 108 or by a separate watchdog process (notshown).

[0060] It will be apparent to those skilled in the art, that the presentinvention as portrayed with respect to FIG. 1, FIG. 5, and FIG. 6, isnot limited to a network connection and server implementation. Forexample, if detectors 110 are retained on client 106, then the fidelityof client's software process 108 may be determined without the presenceof network 104 and server 102. For example, a separate processsubstantially similar to AIS detection unit 114 in execution mayco-exist on client 106 for evaluating responses to detectors, withoutdeparting from the spirit or scope of the invention.

[0061] Referring now to both FIG. 1 and FIG. 5 again, in operation thedetectors 110 are transmitted to client's software process 108 to detectpossible illegal software alterations. In FIG. 1, AIS detection unit 114transmits the three types of detectors 110 described above, whereas inFIG. 5, client detector generator 502 transmits detectors 110 toclient's software process 108. In each embodiment, detector 110 respondseither to positive matches or to both positive and negative matches.Response 112 is bounded by a specified time window within which amatching response is permitted to occur.

[0062] In another embodiment of the present invention, detectors 110 areprovided with a life span or length of time that detector 110 isconsidered active. By employing a life span for detectors 110, anefficiency of usage is provided, such that a predetermined number ofdetectors are active at any given time. This is directed at reducing theprocessing time to evaluate the set of currently active detectors.

[0063] It will be apparent to one skilled in the art, that thedetermination of the detector death rate may be implemented in a varietyof approaches. For example, the death rate of a given detector could bea simple timer, or a function of the number of client responsestransmitted, the number of memory detectors already on server 102, thenumber of positive client responses, the number of audited system calls,or the like, without departing from the scope or spirit of theinvention.

Simultaneous Process Detection

[0064] Securing media from copy by a client software process that may bedirectly involved in the display and control of media has beendescribed. For example, with a video file that is streamed from server102 to client 106, a user may use a media player software program asclient software process 108 to present the video stream. As clientsoftware process 108, the media player is tested for unauthorizedalterations using the AIS detection unit 114 as described above.However, other software processes could compromise the security of thevideo stream once the stream reaches client 106. For example, softwareprocesses that access content directly from the screen buffer and loadthat content into a file (“screen scrapers”) could be used toimpermissibly copy the displayed video.

[0065] To protect against such attacks, the present invention employs anAIS detection unit substantially similar to the one described above. Inaddition, the present invention also employs detectors that aresubstantially similar to detector 400. However, these new detectorsinclude additional information directed at detecting predeterminedprocesses that are running virtually at the same time, thus essentiallyeliminating the screen scraper problem described in the streaming videoexample.

[0066] It will be appreciated by those of ordinary skill in the art,that the invention is not limited to screen scrapers. For example, othervirtually simultaneously running software processes that access sounddata passed to a sound driver in a client (“speaker suckers”) may alsobe detected by the present invention.

[0067] Referring now to FIG. 7, an embodiment of a detector 700 as aninstance of a detector 110 includes a sequence of file system calls thatare substantially similar to the system calls of the detector 400 shownwith reference to FIG. 4. The detector 700 may be classified as one ofthe varieties described above (i.e., memory, self, novel). The detector700 however, includes an additional data field comprising data tospecify the media associated with the file system calls. By employingdetector 700, the AIS is enabled to determine whether a virtuallysimultaneously running process is accessing the media to be protected,thus improving detection of potential unauthorized execution andreplication.

Artificial Epidemiological Control (AEC) Operational Environment

[0068] Unauthorized software alterations may be passed along or even bemass distributed by users and clients, compromising the security of themedia and their stored programs and data on a large scale. Therefore, toaugment the efficacy of the AIS of the present invention describedabove, an embodiment of the present invention includes an ArtificialEpidemiological Control (AEC) component. The AEC component is directedat adaptively responding to widespread unauthorized client behavior bygenerating memory detectors of unauthorized client behaviors, andsharing information about the unauthorized client behaviors among otherservers.

[0069] Because a server will typically distribute media to manydifferent clients, the AEC component is enabled to obtain informationabout previously encountered unauthorized software use from manydifferent clients. With a working memory, virtually identical orsubstantially similar unauthorized software alterations on one clientmay be more efficiently detected on other clients.

[0070] Referring now to FIG. 8, system 800 includes server 102, network104, and clients 106 _(A-C). Clients 106 _(A-C) include softwareprocesses 108 _(A-C) for which the integrity is to be determined.Software processes 108 _(A-C) are substantially similar to clientsoftware process 108 described above. Additionally, clients 106 _(A-C)are each substantially similar to client 106 described above withreference to FIG. 3. Server 102 includes novel database 802,self-fragment database 804, memory fragment database 806, and evaluator808.

[0071] Novel database 802, self-fragment detector database 804, andmemory fragment detector database 806 are coupled to, and incommunication with, client software processes 108 _(A-C), to provide aseries of detectors 110. Client software processes 106 _(A-C) arecoupled to evaluator 808 through network 104 and are enabled to providea series of response(s) 112 to evaluator 808.

[0072] To increase the effectiveness of detection of unauthorizedactivity of software processes 108 _(A-C), memory fragment database 806includes storage of identified unauthorized software behaviors andalterations. The storage of the information about unauthorized softwarealterations and behaviors is typically in the form of memory detector110. Memory detector 110 may be stored in a cluster or grouping based onat least one criterion, such as their tendency to occur together if anillegal process is copied from one client to another client.

[0073] In operation, the AIS detection unit 114 transmits a mix ofself-detectors, novel detectors, and memory detectors through network104 to client 108 _(A) (or 108 _(B or C)). Client software process 108_(A) may provide response 112 that includes a previously unseenunauthorized software alteration or behavior. Response 112 istransmitted to evaluator 808 through network 104, where evaluator 808determines whether there is an inappropriate client response 112 todetector 110.

[0074] Evaluator 808 groups the inappropriate responses together into amemory (not shown) and merges the memory into memory fragment database806.

[0075] The added memory detectors are subsequently sent to other clients106 _(B-C) that are in communication with server 102. In this manner,substantially identical or similar software alterations and behaviorsare rapidly detected throughout clients 106 _(A-C).

[0076] AEC system 800 with its memory fragment database 806 enables theenhanced classification and detection of previously encounteredunauthorized software alterations, behaviors, and unauthorized softwareuse more quickly and more thoroughly than systems without sucharrangements. This strengthening of the AIS system described above is aresult of sending clients 106 _(A-C) many groups or clusters of memorydetectors 110 from the memory fragment database 806, self-fragmentdetector database 804, and memory fragment detector database 806.

[0077] Moreover, when memory detector 110 is matched, the potentiallyunauthorized client 106 _(A, B, or C) may be sent additional memorydetectors 110 associated with originally transmitted memory detector110.

[0078] Client response(s) 112 to additional memory detectors 110 ornovel detectors 110 provide for the classification of client 106 _(A-C)into one of three potential classes. The first class is based on apreviously encountered unauthorized client software process 108 _(A-C)behavior. The second class of client response(s) 112 is based onnewly-discovered unauthorized client software process 108 _(A-C) use,alteration, or behavior. The third class of client response(s) 112 isfor clients that may have demonstrated a short anomalous behavior thathas been observed for an unknown reason, or has not demonstrated itselfthrough its responses as an authorized client.

[0079] When client response 112 is of the first response class, thepresence of positive responses to memory detector 110 is noted. Theoccurrence frequency of memory detector groupings is augmented orincreased in the memory fragment database 806. The frequency tabulationsare retained to provide increased emphasis to unauthorized activitiesthat are more commonly used or appear to be spreading rapidly.

[0080] When client response 112 is of the second response class, amemory detector grouping is generated, with new memory detectorassociations and potentially new detectors. When client response 112 isof the third response class, a memory detector match may be consideredto have provided insufficient for the determination of unauthorizedclient-side behavior.

AIS/AEC Detection Processes

[0081] Referring to FIG. 9, the AIS/AEC Detection process 900 isemployed to detect unauthorized behavior of a client's process, and toshare information about unauthorized behavior with other substantiallysimilar processes. The AIS and AEC Detection process 900 begins, after astart block, at block 902 where detectors are sent to a client process.The detectors are typically sent to the client process in response to arequest for protected electronic media by the client. While the clientprocess is accessing the protected electronic media, a mix ofself-detectors, novel detectors, and memory detectors are also sent tothe client process. The mix of detectors may also include detectors todetermine whether any simultaneously running processes are attempting toscrape or suck the protected electronic media. Once the detectors aresent to the client process, the process moves to block 904.

[0082] At block 904, responses to the sent mix of detectors are receivedfrom the client process. As described above, the responses may be in theform of positive or of negative responses, audited system callfragments, and the like. After block 904, the process control advancesto decision block 906, where it is determined whether the client processhas been altered without authorization, or is attempting to use theprotected electronic media in an unauthorized manner, such that anunauthorized client process behavior exists.

[0083] At decision block 906, the responses from the client process areevaluated according to at least one of the matching rules that determinethe criterion of a response match for determining whether a match is tobe considered validated. At decision block 906, if the determination ofan unauthorized client process behavior is negative, the process controlmoves to block 914, where the life-cycle information for the detectorsis updated. Block 914 is described below in conjunction with FIG. 10.After block 914, the process returns to block 902, where substantiallythe same actions discussed herein are performed.

[0084] Alternatively, if it is determined at decision block 906 that anunauthorized client process is detected, the process control moves toblock 908, where the detection of an unauthorized client processconfiguration is communicated to signify a potential infringement orunauthorized intrusion of the media. The communication of a potentialinfringement could result in terminating a transmission of the media tothe client, a notifying to appropriate parties of the infringement,terminating the unauthorized client process, and the like. Uponcompletion of block 908, the process control moves to block 909.

[0085] At block 909, the memory database is updated. The process controlproceeds to block 910, where detector database information is sharedbetween servers. Block 910 is described in FIG. 11 and the relateddiscussion. Upon completion of the block 910 processing, the logicalflow of AIS and AEC process 900 proceeds to block 912.

[0086] At block 912, updated detectors are sent to substantially similarclient processes on other clients. In this way, other client processesmay be examined for identical or substantially similar unauthorizedclient behavior, thereby more rapidly detecting inappropriate orunauthorized behavior across several client processes. Additionally, atblock 912, the original determined unauthorized client process may besent updated detectors to provide further probing of unauthorizedactivities or usages of the electronic media.

[0087] Upon completion of block 912, the process control moves to block914, where substantially the same actions discussed above are performed.

Detector Life-Cycle Update Process

[0088] Referring to FIG. 10, a process (described above with referenceto block 914) begins at decision block 1002 where a determination ismade whether a detector has reached its end of life.

[0089] If the determination at decision block 1002 is affirmative, theprocess control advances to block 1004 where the detector is terminatedor killed. Upon completion of block 1004, the process control returns toblock 902 (shown in FIG. 9) where substantially the same actionsdiscussed above are performed.

[0090] Alternatively, if it is determined at decision 1002 that thedetector has not reached an end of its life cycle, the process controladvances to decision block 1006, where a determination is made whetherthe unauthorized client process behavior has been encountered before.

[0091] At decision block 1006, if the determination is affirmative,process control is transferred to block 1008. At block 1008, thefrequencies of observation of detectors are updated based on thefrequencies of identified unauthorized client process behaviors. Thefrequency tabulations are retained to provide an increased emphasis onmore commonly employed or more rapidly spreading unauthorized clientprocess behaviors. The result of block 1008 may be to adjust thetransmission frequency of particular detectors or mixes of detectorssent at block 912 in FIG. 9. Upon completion of block 1008, the processcontrol advances to block 1014.

[0092] Alternatively, if it is determined at decision block 1006 thatthe unauthorized client process has not been encountered before, theprocess control is transferred to decision block 1010, where adetermination is made as to whether the unauthorized client behavior isnewly discovered to this process.

[0093] At decision block 1010, if the determination is affirmative, theprocess control moves to block 1012. At block 1012, new detectors arecreated, with accompanying matching rules, to detect future occurrencesof this new unauthorized client process behavior. Upon completion ofblock 1012, the process continues at block 1014.

[0094] Alternatively, if it is determined at decision block 1010 thatthe unauthorized client process behavior is not new or novel, theprocess control moves to block 1014. As part of the determination thatthe unauthorized client process behavior is not new or novel, decisionblock 1010 also determines whether the unauthorized behavior is besubstantial enough for the detection of infringements, alterations ofelectronic media, and the like.

[0095] At block 1014, the changes to the frequency of detectors, andinformation about new detectors are retained in a database.Additionally, at block 1014, the life span information for detectors isupdated in the database of detectors. Upon completion of block 1014, theprocess control returns to block 902 (shown in FIG. 9) wheresubstantially the same actions discussed above are performed.

Sharing Memory Detector Databases

[0096] Referring to FIG. 11, a process 1100 begins after a start block,at block 1102, where memory detectors from a set of memory databases aregrouped along with the detectors' associated matching rules. Thegroupings are sent to other servers. After block 1102, process controlmoves to block 1104.

[0097] At block 1104, memory detector groupings from the memorydatabases of other servers are received. The process control then movesto decision block 1106, where evaluations of the received detectorgroupings are performed.

[0098] If it is determined at decision block 1106 that the receivedmemory detector matches a detector in at least one of the recipient'smemory databases, given the recipient's matching rules, and thus is nota new detector, process control moves to block 1110. At block 1110,detectors that are matched, and determined to already exist in some formin one or more of the recipient's databases, are discarded. Discardingduplicate detectors avoids problems that may arise if the duplicatedetectors have associated with them different matching algorithm(s)(rules) than the algorithm(s) of the recipient's detectors. Uponcompletion of block 1110, the process returns to block 912 in FIG. 9.

[0099] Alternatively, at decision block 1106, if it is determined that areceived memory detector is new to the recipient's memory database, theprocess control proceeds to block 1108. At block 1108, the new memorydetector and its associated matching rules are retained by merging theminto the recipient's pre-existing memory database. In this manner, thesharing of detectors between databases of detectors improves thelikelihood of detecting unauthorized client process behaviors on alarger scale. Upon completion of block 1108, the process control returnsto block 912 in FIG. 9 to perform other actions.

AEC Multi-Server Communications

[0100] Referring to FIG. 12, a multi-server communications AEC process1200 includes servers 102 _(X-Z), and network 104. Each server 102_(X-Z) includes an AEC unit 1208 _(X-Z). Servers 102 _(X-Z) are eachsubstantially similar to server 102 portrayed with reference to FIG. 2.Although not shown, each server 102 _(X-Z) may be in communication witha plural number of clients. Furthermore, a network arrangement ofservers and clients may range from mostly overlapping the communicationswith clients to communicating with distinct client sets. Each server 102_(X-Z) is coupled to network 104, which provides a communications pathbetween each other server 102 _(X-Z).

[0101] It will be appreciated that the configuration of networks andservers may comprise a vast number of such interconnected networks,servers, and clients (not shown) and other interconnections may beemployed without departing from the spirit or scope of the presentinvention.

[0102] In operation, during an update period, server 102 _(X) transmitsthrough network 104, memory detector group(s) 1202 _(X) to servers 102_(Y) and 102 _(Z), while server 102 _(Z) transmits through network 104memory detector group(s) 1202 _(Z) to servers 102 _(X) and 102 _(Y). Asshown in the figure, when a server, such as server 102 _(Y), currentlydoes not have new memory detector group(s) to share, that server remainsa recipient of other servers' memory detector group(s) 1202 _(X,Z).

[0103] Although the present description refers to the sharing of memorygroups between servers at substantially the same time, it is understoodthat other embodiments may be utilized, e.g., each server may share itsmemory groups at some random update period that is independent of theother servers' update period, without departing from the spirit or scopeof the invention.

[0104] The establishment of memory detector databases enables servers toincrease the speed and thoroughness of detecting previously seen illegalclient software configurations. The multi-server communications AECarchitecture 1200 scales up this benefit in a more encompassing approachto networks of servers by enabling the sharing of detectors betweenservers. This embodiment of the present invention therefore provides forthe obstruction of the spread of unauthorized software alterationsbetween clients that communicate with other servers on the AEC network.

[0105] If server 102 _(X-Z) on network 104 receives the memory detectorgroups 1202 _(X-Z), the server's AEC unit 1208 evaluates them againstthe recipient's self-database according to the recipient server'smatching rule.

[0106] Referring now to FIG. 13, a memory detector evaluation system1300 includes server 102 and memory detector groups 1202. Server 102 isin communication with other servers as shown in FIG. 12, and receivesmemory detector groups 1202 from those servers as described above.

[0107] Server 102 includes AEC unit 1208, which in turn includes a setof matching algorithm(s) (rules) 1306, garbage collector process 1302,and portions of self-fragment database 804 and memory-fragment database806. Self-fragment database 804 is coupled to and communicates withgarbage collector process 1302 and memory-fragment database 806.Moreover, self-database 604 is coupled to a set of matching algorithms(rules) 1306.

[0108] In operation, because each server 102 that shares memorydetectors may have a different set of matching rules 1306 from otherservers 102, an incoming memory detector group 1202 is tested againstself-fragment database 804 of the recipient server. If memory detector110 within memory detector group 1202 is matched to a fragment in therecipient's self database, according to the recipient's set of matchingrules 1306, that detector 110 _(G) is transmitted to garbage collectorprocess 1302 where detector 110 _(G) is discarded. This avoids thelikelihood of false positive detections that may arise due to varyingmatching rules.

[0109] If memory detector 110 within received memory detector group 1202is determined to be unmatched to recipient's self-fragment database 804,memory detector 110 is transmitted to memory-fragment database 806 whereit is merged into server's 102 pre-existing set of detectors. The resultof this exchange of memory detector groups 1202 between servers enablesthe scaled-up detection of previously seen illegal softwareconfigurations and an improved likelihood of obstructing spreads ofillegal software alterations between more clients.

Combined AIS/AEC Embodiment

[0110] Referring to FIG. 14, an integrated AIS/AEC system 1400 includesservers 102 _(X-Y), network 104, and clients 106 _(A-C). Clients 106_(A-C) include software processes 108 _(A-C), respectively. Server 102_(X) includes novel database 802 _(X), self-fragment database 804 _(X),memory fragment database 806 _(X), evaluator 808 _(X), and AEC unit 1208_(X) as described above with reference to FIGS. 8, 12, and 13. Server102 _(Y) includes novel database 802 _(Y), self-fragment database 804_(Y), memory fragment database 806 _(Y), evaluator 808 _(Y), and AECunit 1208 _(Y) as described above with reference to FIGS. 8, 12, and 13.

[0111] Servers 102 _(X-Y) are coupled to network 104 and communicatedetectors 110 to the respective clients' software processes 108 _(A-C).As shown, server 102 _(Y) is enabled to communicate with clients 106_(B-C), while server 102 _(X) is enabled to communicate with client 106_(A).

[0112] Clients 106 _(A-C) are coupled to the network 104 and communicateresponse(s) 112 to the appropriate server 102 _(X or Y) through network104.

[0113] Moreover, servers 102 _(X-Y) communicate with each other throughnetwork 104 to provide sets of memory groups 1202 _(X-Y) to the otherserver 102 _(X or Y).

[0114] The integrated AIS/AEC system 1400 enables adaptation over timeby providing for the identification of previously unseen, andunauthorized, software operations within a client software process 108as “non-self” actions while providing for the sharing throughout thenetwork of servers of previously seen unauthorized software operations.

[0115] The AIS component of integrated AIS/AEC system 1400 enables thedetection of a broad range of security-compromising software activity aswell as the detection of more direct hostile attacks upon the integrityof the system 1400. The employment of self, memory, and novel detectors110, in a “dialog” between server 102 _(X-Y) and client 106 _(A-C)enables detection of not only attempts to subvert software but alsoattempts to subvert the AIS itself. Moreover, by providing detectordeaths, the impact of the AIS components' processor usage may beminimized.

[0116] The AEC component of the integrated AIS/AEC system 1400 enablesdetection of the spread of compromised software as well as thedevelopment of data attacks by sharing information between servers 102_(X-Y). The employment of databases of detectors (802 _(X-Y), 804_(X-Y), and 806 _(X-Y)) is directed at enhancing the efficiency ofidentification of previously encountered subversions, and the sharing ofthis information between servers provides broader protection among apopulation of clients 106 _(A-C).

[0117] It will be appreciated that configuration of networks, servers,and clients may comprise a vast number of such interconnected networks,servers, and clients, and other interconnections may be employed withoutdeparting from the spirit or scope of the invention. The embodimentportrayed with reference to FIG. 14 enables a less complicatedpresentation of an embodiment of the present invention than a moreintricate network.

Other Specific Embodiments of the Invention

[0118] In light of the present disclosure, the present invention hasidentified other specific embodiments that may be directed towardsimproving the operational efficiency or speed with which the inventionidentifies a security-compromising client configuration.

[0119] One such embodiment significantly increases the efficiency of thepresent invention by maximizing the amount of non-self space covered bya fixed number of non-self detectors. Typically, to detect abnormalbehavior, non-self detectors may need to be generated and compared withlogged file system calls to determine the presence of potential matches.For a fixed detector length, the stringency of matching is determined bythe stringency of the matching rules. For example, an illustrativedetector length of say eight system calls, a matching rule that wouldrequire two consecutive file system calls to be substantially identicalto the logged system call fragment would be less stringent than amatching rule that requires seven of the eight consecutive system callsto match. Thus, a less stringent detector-matching rule would match alarger number of logged sequences, and consequently cover a larger areaof non-self space. By cyclically generating detectors withever-increasing stringency of matching rules, the inventors haveidentified, and the present invention specifically includes, that thenon-self space may be covered more efficiently. That is, instead of allthe detectors employing the same matching rule, and thereby covering thenon-self space in equally sized partitions, the present invention takesadvantage of the heterogeneity of non-self space. In this approach,different detectors with different matching rules, allow certain largerareas of non-self space to be covered with a relatively small number oflow-stringency-rule detectors, and certain small partitions or crevicesof non-self space to be covered with higher-stringency-rule detectors.

[0120] In yet another such embodiment of the present invention, thespeed is increased for evaluating the presence of a match between thedetector and log fragment, by employing a comparison algorithm such asthe Rabin-Karp algorithm and the like. Algorithms such as the Rabin-Karpemploy prime numbers and sliding windows on the system calls toconsiderably shorten the amount of time required to evaluate stringmatches.

[0121] In yet another such embodiment of the present invention, greaterefficiency is provided by developing the matching rules to minimize thenumber of comparisons necessary to identify a security-compromisingclient configuration. In this embodiment, an adaptive rule-learningalgorithm is employed. Specific matching rules are evolved throughtraining on the self-data, and these rules are then employed to morerapidly identify unauthorized client configurations. More general rulesmay be extracted from analysis of the self-database and directed atcovering a larger portion of the search space by generating rules thatmatch key elements of recurring patterns of system calls, rather thanspecific system calls. As described above, the ‘*’ token provides anexample of the generation of a more generalized rule.

[0122] Such generalized rules may be developed to describe larger partsof the non-self space, to cover as large a portion of the space beingsearched as feasible with the least number of rules, thus improving theefficiency of the detector comparisons.

[0123] Embodiments of the present invention include program operationsstored on a machine readable medium. A machine readable storage mediumincludes any mechanism that provides (i.e. stores and/or transmits)information such as computer readable instructions, data structures,program modules, or other data; in a form readable by a machine (e.g. acomputer). For example, a machine readable medium includes read onlymemory (ROM), random access memory (RAM), magnetic storage media,optical storage media, flash memory devices and other solid stateelectronic memory devices, electrical, optical, acoustical or otherpropagated signals (e.g. carrier waves, infrared signals, digitalsignals, etc.) etc.

[0124] In the foregoing specification, the present invention has beendescribed with reference to specific exemplary embodiments thereof. Itwill however be evident that various modifications and changes may bemade thereto without departing from the broader spirit and scope of theinvention as set forth in the appended claims. The specification anddrawings including specific embodiments described are accordingly, to beregarded in an illustrative rather than a restrictive sense. Manyembodiments of the invention can be made without departing from thespirit and scope of the invention. The invention resides in the claimshereinafter appended.

We claim:
 1. A method of protecting machine readable media fromunauthorized storage or copying, comprising: sending a detector to aclient process; receiving a response to the detector from the clientprocess; detecting a presence of an unauthorized software behavior onthe client based upon the response and a matching rule that isassociated with the detector sent; and updating a database of detectorsfor a previously unseen and unauthorized behavior of the process suchthat the database of detectors evolves over time.
 2. The method as inclaim 1, wherein the sent detector includes at least one of aself-detector, a memory detector, and a novel detector.
 3. The method asin claim 1, wherein the sent detector further comprises detecting thepresence of an unauthorized substantially simultaneously executingclient process.
 4. The method as in claim 1, wherein the sending of thedetector further comprises varying a sequence length of a computersystem call within the detector such that the meaning of the detector isobscured.
 5. The method as in claim 1, wherein the sending of thedetector further comprises encoding numerically the detector such thatthe meaning of the detector is obscured.
 6. The method as in claim 1,wherein the matching rule includes a criterion for each field in thedetector that is to be matched before a match is validated, wherein eachfield includes a sequence of at least one computer system calls.
 7. Themethod as in claim 1, further including sending the detector to detectpreviously unseen and unauthorized behavior to another client process.8. The method as in claim 1, further including: exchanging sets ofmemory detectors between a server and another server during an updateperiod; evaluating the received set of memory detectors against eachserver's self database and a set of matching rules; discarding memorydetectors in the received set of memory detectors that match anotherdetector in each server's self database, wherein a false positivedetection is minimized; and merging each new retained memory detectorfrom the received set of memory detectors with each server's memorydatabase, wherein the exchange of the sets of memory detectors betweeneach server obstructs the spread of unauthorized copying and corruptionof electronic media.
 9. A method for obstructing unauthorized copyingand corruption of media between clients that communicate over a networkof servers, comprising: exchanging a set of memory detectors betweenservers during an update period; evaluating each received set of memorydetectors against each server's self database and a set of matchingrules; discarding each detector in the received set of detectors thatmatch another detector in each server's self database; and merging a newretained detector from each received set of detectors with each server'smemory database, wherein the exchanging of the set of memory detectorsprevents unauthorized copying and corruption of media.
 10. The method asin claim 9, wherein the set of detectors include at least one of aself-detector, a memory detector, and a novel detector.
 11. The methodas in claim 9, wherein the set of detectors enable the detection of thepresence of an unauthorized substantially simultaneously executingclient process.
 12. The method as in claim 9, wherein the exchanging theset of memory detectors further includes varying a sequence length of acomputer system call within each detector such that each detector isobscured.
 13. The method as in claim 9, wherein the exchanging the setof detectors includes encoding numerically the detector such that themeaning of the detector is obscured.
 14. The method as in claim 9,wherein the matching rule includes at least one criterion for each fieldin each detector that is to be matched before a match is validated, andwherein each field includes a sequence of at least one computer systemcalls.
 15. A method of providing detection of machine-readable mediafrom an unauthorized usage, the method comprising: evaluating a responsefrom a process to a series of behavioral questions; detecting anunauthorized behavior of the process based on the evaluating; andcommunicating the unauthorized behavior of the process among a pluralityof processes, wherein detection of unauthorized usage is enhanced.
 16. Asystem to protect media from unauthorized usage, the system comprising:a server to send media to a client; and a program to perform actionswhen executed that include: sending a detector to the client, receivinga response to the detector from the client, detecting a presence of anunauthorized process on the client based on the response and a matchingrule associated with the detector, and updating a database of memorydetectors for a previously undetected and unauthorized process on theclient such that the database of memory detectors evolves over time. 17.The system as in claim 16 further including employing the client toaccess the media.
 18. The system as in claim 16, wherein the sending ofthe detector includes adjusting the frequency of a class of detectorssent in response to changes in responses from each client, such that theclass of detectors includes at least one of a self-detector, a memorydetector, and a novel detector.
 19. The system as in claim 16, whereinthe updating further includes eliminating detectors in the database thatexceed a predetermined detector life span.
 20. The system as in claim16, wherein the matching rule includes at least one criterion for afield in the detector to be matched before a match is validated, andwherein the field includes a sequence of at least one computer systemcalls.
 21. The system as in claim 16, wherein the detecting includesexecuting a Rabin-Karp algorithm of prime numbers and a sliding windowacross the response and the detector.
 22. A computer readable mediumhaving stored thereon a data structure to provide a detector pattern foruse in data integrity of machine-readable media, the data structurecomprising a plurality of data fields associated with a matching rule tovalidate a match of the plurality of data fields from a response to thedata structure, and wherein each of the plurality of data fieldscomprises a computer system call.
 23. A machine readable medium thatprovides instructions which, when executed by at least one processor,cause said processor to perform operations comprising: sending adetector to a client process; receiving a response to the detector fromthe client process; detecting a presence of an unauthorized behavior onthe client based upon the response and a matching rule that isassociated with the detector sent; and updating a database of memorydetectors for a previously unseen and unauthorized behavior of theclient process such that the memory database evolves over time.
 24. Themedium as in claim 23, wherein the detector further includes at leastone of a self-detector, a memory detector, and a novel detector.
 25. Themedium as in claim 23, wherein the detector detects the presence of anunauthorized substantially simultaneously executing client process. 26.The medium as in claim 23, wherein the sending of the detector furtherincludes varying a sequence length of computer system calls within thedetector such that the meaning of the detector is obscured.
 27. Themedium as in claim 23, wherein the sending of the detector furtherincludes encoding numerically the detector such that the meaning of thedetector is obscured.